Street trees may reduce the risk of depression

Street tree planting in residential areas of cities can serve as a nature-based solution to reduce the risk of depression with added benefits of also addressing climate change and biodiversity loss. This should be taken into account by urban planners, health professionals, and conservationists, the researchers urge in a paper recently published in Scientific Reports.

Depression, especially in urban areas, is on the rise, now more than ever. Mental health outcomes are influenced by, among other things, the type of environment where one lives. Former studies show that urban greenspace has a positive benefit on people experiencing mental ill health, but most of these studies used self-reported measures, which makes it difficult to compare the results and generalise conclusions on the effects of urban greenspace on mental health.

An interdisciplinary research team addressed this issue by choosing an objective health indicator: prescriptions of antidepressants. To find out whether a specific type of ‘everyday’ green space – street trees dotting the neighbourhood sidewalks – could positively influence mental health, they focused on the questions, how the number and type of street trees and their proximity close to home correlated to the number of antidepressants prescribed.

The researchers were able to identify the association between antidepressants prescriptions and the number of street trees at different distances from people’s homes. Results were controlled for other factors known to be associated with depression, such as employment, gender, age, and body weight.

More trees immediately around the home (less than 100 meters) was associated with a reduced risk of being prescribed antidepressant medication. This association was especially strong for socioeconomically disadvantaged groups.

“Our finding suggests that street trees – a small scale, publicly accessible form of urban greenspace – can help close the gap in health inequalities between economically different social groups,” says lead author of the study Dr Melissa Marselle. “This is good news because street trees are relatively easy to achieve and their number can be increased without much planning effort.”

And it’s not only human health which could benefit. “We propose that adding street trees in residential urban areas is a nature-based solution that may not only promote mental health, but can also contribute to climate change mitigation and biodiversity conservation,” says senior author Prof Aletta Bonn, who leads the department of ecosystem services at UFZ, iDiv and FSU.

“To create these synergy effects, you don’t even need large-scale expensive parks: more trees along the streets will do the trick. And street trees are a relatively inexpensive nature-based solution for climate and health promotion.”

Image credit: Philipp Kirschner

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